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TOLUENE FROM p-TOLUIDINE                  163
potassium iodide solution.    Effervescence occurs  and  a  dark
coloured liquid separates out.    This is iodobenzene.
C0HGN,S04H + KI = C0H6I + N2 + KHSO4.
5.    Dissolve the substance in water and warm gently.    Effer-
vescence occurs and a dark coloured oil separates, which has the
smell of phenol.    When effervescence ceases, cool and shake
up with a little ether.    Decant the ether into a dry test-tube.
Evaporate the ether and test the residue for phenol, see p. 179.
Cyif.NoSOJi + FLO = C0H5OH + H2SO4 + N2.
6.    Dissolve the substance  in cold water and add it to a
solution of phenol in caustic soda, drop by drop.    An orange
crystalline precipitate of hydroxyazobenzene is formed.    Repeat,
using /3-naphthol in place of phenol.    A scarlet precipitate is
CGH6N,,SO.,H + C(5H,ONa - C0Hr,N:N.C0H4ONa + Na,SO4
-f 2NaOH                                          + 2H20.
7.    Dissolve in cold water and add a few drops of aniline,
and shake up.    Diazoaminobenzene separates out as a yello\v
crystalline precipitate.
C(iH5N,S04H + C0HSNH3 = C0HfiN:N.NHC0H5 + H2SO4.
8.    Heat o'5 gram of the dry substance on an iron tray.    It
decomposes with slight explosion.
Any of the diazo-compound which remains over should be
dissolved in water and poured away.    See Appendix^ p. 282.
Toluene from p-Tohiidine, C(iH-.CH3,
Kricclliindcr, Her., 1889, 22, 587.
10 I>TIYJS. /;-toluidinc.
30 c.c. cone, hydrochloric acid (in 60 c.c. water).
7-5    sodium nitrite (in powder).
15      of caustic soda (in 50 c.c. water).
30     stannous chloride (in 75 c.c. water).
The /Moluidine, which is placed in a beaker, is dissolved in
the hydrochloric acid by warming and is then cooled under the
M 2